In large-scale agricultural production (i.e., farming), it is common practice to fertilize the soil with a liquid fertilizer.
Often, this is done using a knife or disc opener on an applicator or planter, as well known in the art, with a plurality of distribution lines from the flow divider--preferably one associated with each knife or disc opener--used to distribute the liquid fertilizer. A supply of the liquid fertilizer typically is contained in a large tank which is supported on or pulled by the agricultural machinery, and the liquid fertilizer is pumped from the supply tank through a conduit to a flow divider distributor which divides the flow of fertilizer into a plurality of streams, with one stream flowing to each point of placement behind the knife or disc opener.
In general, it is important for the flow of fertilizer to be divided uniformly among the several flow streams. Otherwise, some areas of the ground will receive more fertilizer than is required or can be used (hence wasting fertilizer) and other areas will receive less fertilizer than required (hence causing poor crop growth in those areas).
Previously, it has been known to use a standard "manifold" system to distribute the liquid fertilizer. Such a manifold system has a single inlet and multiple outlet ports receiving flow from a central manifold plenum or chamber. In order for such a manifold system to distribute flow accurately, an appropriately sized orifice is provided in the flow path of each outlet port, thereby creating a minimum pressure and promoting even distribution between the various ports. Unfortunately, these orifices typically are each sized for a specific, generally narrow flow range. Therefore, variation in fertilizer flow rate, e.g., due to variation in application speed or rate, requires the operator to suspend the fertilizer application and manually change the external orifices to match the new required flow rate. Furthermore, these orifices are subject to clogging.
Alternatively, automatically adjusting flow dividers, which operate over a wider range of fertilizer flow rates, have also been used. These previously known, automatically adjusting flow dividers utilize separate needle valves each regulating the flow through a respective exit flow port, and each needing to be calibrated independently. All of the valve needles are linked to a central rod; the central rod, in turn, is held against a spring and diaphragm to control its axial movement and hence the axial positioning of each of the individual port needles. This design has proven to be somewhat cumbersome, and therefore inefficient because the relatively large number of parts and the required calibration of each of those parts increases the cost of the divider and decreases its serviceability--particularly when in the field.